A conventional liquid crystal display consists of a thin film of a liquid crystal material sandwiched between two transparent glass plates. The glass plates are hermetically sealed together to contain the liquid crystal material and to prevent oxygen and moisture from chemically attacking and degrading the liquid crystal material. In such displays, a matrix of picture elements is positioned within a sealed region to form a display area. The picture elements are constructed of transparent electrodes disposed on surfaces of the glass plates within the sealed cavity. Drive circuits which are electrically connected to the picture elements are located external to the sealed region of the display.
The drive circuits are typically located on circuit boards positioned around the liquid crystal display. Such drive circuits are electrically connected to the picture elements via wires extending from the drive circuits to electrical contact terminals disposed on the liquid crystal display. Interconnections positioned on the liquid crystal display electrically connect the electrical contact terminals to corresponding picture elements.
Several configurations of electrical contact terminals and interconnections for liquid crystal displays are known in the art. One type of prior art liquid crystal display positions the seal a distance in from the glass plate edges. Electrical contacts are then located in a region between the glass plate edges and the seal on the same surface of the glass plate as the picture elements. The electrical contacts are connected to switching elements positioned in the display region by row and column conductors which are coated on the glass plate and extend into the sealed display region.
An example of this type of display configuration is disclosed in U.S. Pat. No. 4,832,457. A disadvantage of such a configuration is that the active display area cannot extend to regions proximate the edges of the glass plates because these peripheral regions are utilized to accommodate the placement of the electrical contact terminals. Thus, such a configuration is not suitable for liquid crystal display applications requiring the largest possible active display area, such as in tiled modular display systems.
Another prior art configuration is disclosed in U.S. Pat. No. 5,067,021 which is assigned to the assignee of the present invention and which is hereby incorporated by reference. U.S. Pat. No. 5,067,021 discloses a modular flat-panel liquid crystal display which can be formed by a polymer dispersed liquid crystal material sandwiched by two glass plates. No perimeter seal is required when polymer-dispersed liquid crystal material is used. Drive circuits are connected to the picture elements in the display region by row and column conductors and wrap-around edge interconnects.
The wrap-around edge connects are made by known metalization and photolithographic techniques on an adhesive side of a thin, insulating tape approximately 0.001 inches in thickness. The tape is then wrapped around an edge surface. Although such a configuration achieves a relatively large module display region, the display panels are relatively expensive and difficult to manufacture.
There is a recognized need for a liquid crystal device configuration that can position picture elements in close proximity to the edges of the liquid crystal display at a reasonable cost.